Intelligent Transport Systems (ITS) have attracted increased attention in recent years. Intelligent Transport Systems include telematics and all types of communications in vehicles, between vehicles, and between vehicles and fixed locations.
In Vehicle to Vehicle (V2V) communications, cars may distribute data messages to surrounding cars using Proximity Services (ProSe) broadcast. The same principle has also been proposed for Vehicle to Person (V2P) communications, where cars exchange messages with the mobile phones of vulnerable road users such as pedestrians and cyclists. It has also been proposed to use ProSe communications for Vehicle to Infrastructure (V2I) communications, where cars exchange messages with roadside equipment to e.g. receive information on speed limits, applicable road signs, find nearby parking spots, traffic lights, etc.
The assumption with using ProSe communications for V2I communications is that there is a Road Side Unit (RSU) that uses ProSe to communicate with the cars. An RSU may e.g. be fitted on top of a street light to broadcast the status of the street light to nearby cars.
The application of RSUs, however, yields several disadvantages. The application of RSUs is expensive. A lot of new RSUs have to be installed as the range of ProSe communication is generally small. Also all these RSUs have to be maintained. Another disadvantage is that the communication with the RSU is inefficient. Traffic messages from a car should normally not be directed directly to the nearby traffic infrastructure component (e.g. the traffic light, street sign, information panel), but to the traffic control systems that control these road side units. These controllers often control a larger area and are located more remotely from the traffic infrastructure components. For example, the controllers for a traffic light may not be reachable using ProSe broadcast by a car that stops in front of the traffic light.
One way of reaching the controllers is by means of ETSI TS 102 636-3, Intelligent Transport Systems (ITS); Vehicular Communications; GeoNetworking; Part 3: Network architecture. ITS messages are described to be routed using GeoNetworking. To that end, geographic information is added in a header of the ITS message by the source of the message in order to route the message to a destination that is relevant for that location. This geonetworking assumes a dedicated geonetworking protocol and routers that can route on the basis of this geonetworking protocol (with the header).